1. Field of the Invention
The present invention relates generally to mechanical devices used in surgical procedures to obtain ligation or hemostasis and more particularly, to a ligation clip used during surgery to clamp vessels or ducts such as a cystic artery or cystic duct and thereby obtain ligation.
2. Description of the Prior Art
It will be appreciated by those skilled in the art that the use of ligation clips to control bleeding during surgical procedures is well known. As described, for example, in U.S. Pat. Nos. 4,976,722 and 4,979,950, prior art clips are generally formed of metal wire usually a titanium alloy having a U-shaped cross section. Such prior art clips often include a grooved pattern machined into the inner or clamping surfaces of the clip in an attempt to enhance the ability of the clip to remain in position after it is closed around the vessel. Application of the clip to the vessel is often effected by means of a crushing action produced by a clip applier such as that disclosed in U.S. Pat. No. 5,030,226. Such crushing action permanently deforms the clips making them difficult to remove or reposition.
Prior art surgical ligation clips have several inherent problems. For example, the force applied by the clip to the vessel can be variable and inconsistent from one clip to the next because of the variation in crushing force applied to the clip by the user. Further, prior art clips have a tendency to slip off the end of the blood vessel stub (i.e., perpendicular to the axis of the vessel) to which it has been applied because of the low coefficient of friction associated with the clip and lack of adequate restraining force provided by the clip. Because of this, separation of the clip from the vessel to which it has been applied after the wound has been closed is not uncommon. A related problem found in the prior art is the fact that the ligation or restraining force offered by crushed clips vary along the length of the clip decreasing toward the open end. Thus, the section of the vessel near the open end of the clip can be inadequately ligated.
It is also common in the prior art to form and crush the clip only at the time of its application to the targeted vessel. In order to ligate a vessel with a crush clip, it is required that the inside clearance dimension of the clip prior to crushing be larger than the vessel. This does not lend itself to clip appliers designed to pass through small 5 mm trocars. The applier must be inserted through a trocar placed through the patient's external tissues and into the surgical field. Thus, prior art ligation clip appliers used in laparoscopic procedures typically consist of a 10 mm diameter clip applier that can fit only through a trocar having a 10 to 11 mm diameter entry port. Because one goal of laparoscopic surgery is to minimize the size of the entry wound, a surgical ligation clip and clip applier that can be used within a 5 mm or even a 2.5 mm diameter port is highly desirable. One approach for providing a smaller diameter endoscopic clip applier is disclosed in U.S. Pat. No. 5,601,573 to Fogelberg et al. The '573 patent applies a complex manipulation to advance the clip in a closed position and then open the clip prior to placement. To place a clip, the '573 patent uses an overly complex multi-stage trigger mechanism for actuating a clamping jaw and advancing the clip.
The clip described in the '573 patent is a spring-action clip that suffers from several deficiencies. First, the clip has little or no pre-load, which means that vessels or ducts of very small diameter have little or no ligation force applied. Vessels such as cystic arteries often fall into this small category. Secondly, the clip of the '573 patent provides for only a single point of contact of the clip on the vessel. This requires a surgeon to use multiple clips to ensure ligation in case one clip is dislodged from the vessel by activity of the patient during a post-surgery period. The clip of the '573 patent is also very narrow in width and thereby has little or no utility for ligating vessels or torn tissue in an end-on or head-on application technique such as described in U.S. Pat. No. 6,350,269 to Shipp et al.
The '269 patent describes a clip that has many advantages for use in trocar entry wounds of 5 mm and smaller. The '269 clip includes a vessel clamping arm, a vessel support member, and tension coils integrally joining the arm and support member. The vessel support member includes two legs that are substantially parallel and joined by a bend section at the distal end of the clip. The vessel clamping arm includes a single leg with a bend section at the distal-most end of the clip and terminates at the free end of the single wire forming the clip at a point between the distal and proximal most ends of the clip. Thus, the side of the clip of the '269 patent which contains the single leg of the clamping arm may subject the vessel being ligated to greater shear than necessary. The clip shown in FIG. 9 of the '269 patent can provide inadequate ligation for very small vessels that can be woven between the legs of the vessel support member and the leg of the clamping member because of spaces between these three legs. The clip described in the '269 patent is not symmetric in applying a ligating force passing through the clip parallel to the longitudinal axis. Thus, when the clip is loaded into a clip applier, care must be taken to ensure that the clip is loaded in the proper orientation.
Many clips of the prior art have an exposed free end which is small in dimension and can be caught or snagged on tissue during either the clip placement procedure or when in some circumstances the clip has to be removed. The clip of the '573 patent and the crush clips of the prior art are examples of clips that can snag tissue upon installation. The clip of the '269 patent has a free end generally pointed in the proximal direction and is an example of a clip that could snag tissue upon a removal procedure.
What is needed then is a spring-loaded ligation clip with a pre-load that supplies a ligating force to very thin vessels that has two points of ligation throughout the usable length of the clip. What is also needed is a spring clip having ligating members that do not interfere with tissue during the installation process so that tissues of varying thicknesses can be ligated throughout the usable length of the clip. What is further needed is a clip that does not have a free end that could snag and become entangled in tissue during installation or removal procedures. What is also needed is a clip with upper and lower support members that are symmetric to reduce or eliminate loading errors. A clip that satisfies one or more of these needs is described.
Further objects, features, and advantages of the present invention will be readily apparent to those skilled in the art upon a reading of the following disclosure when taken in conjunction with the accompanying drawings.